Process of dephosphorizing iron in an open-hearth furnace



a 7 UNITED STATES JACOB REESE/OF ALLEGHENY;PENNSYLVANIA. I

PATENT PROCESSOF DEEHOSPHOBIZlNG IRON l N ANoPEN-HEARTtl FUR-MACE.

SPECIFICATION forming part of Letterslatent No. 284,233, dated September 4,1883. 7

' Application filed March 8, 1883. (X specimens.)

To all whontit may con/0617 1 Beit known that I, J AOOB REEsE, a citizen of the United States, residing at Allegheny, in

the county of Allegheny and State of Pennsyl- .I atsuch a high temperature as existed in such afurnace. In the course of my investigation of the subject'I discovered that when phosphorus was removed from molten iron itwas oxidized to phosphoric acid, (F 0 which united with a base oxide of iron or oxide of calcium, forming a phosphate, and as the sand lining was composed principally of silicic acid (SiO,,) the silicicacid possessing a greater affinity for the oxide of 1 iron and oxide of calcium than phosphorushas, when silicic acid was present in a free state, it robbed the phosphate of its base oxide of iron or oxide of;calcium and the phosphorus went back into the metal, because it could not exist under the cono ditions, except as aphosphate in the slag or as a phosphide in the metal. I therefore concluded to dispense with the acid lining, and ,in place thereof use a calcareous basic lining in order to secure a more perfectbasic slag, so-

i I 5 that the phosphate, ,when once formed, might t ready for use the fire is lighted and it is slowly be held in the slag without coming in contact with the decomposing influence of silioic acid. In my further researches in this line I discovered that when. carbonic oxide (C t passed 40 through a slag having a phosphate in itthe carbonic oxide robbed the phosphate of its oxygen and the phosphide returned to the. metal, I then conceived the idea of eliminat ingthe carbon. entirely, and then, in the absence of silicic acid and carbonicoxide, and

in the presence of a basic lining and a basic bath, dephosphorizing the metal and removing the phosphate with the slag, and I shall now describeand definitely limit theprcsent 5o invention.

generators, stack, and gas-producers and hav .ing the metal chamber. lined with a lime-or the furnace being fully and clearly set forth in patent issued tome November 15, 1881, No.

Dephosphorization was not at? pure and simple, as practiced in .thefopen hearth, and is conducted as follows: I V l The open-hearth furnace is furnished with its usual appurtenances such as valves, re-

magnesian-lime lining, the method of preparing,vindurating, and putting the lining into 249,548, and pending application filed March 14, 1881, Serial No. 28,274Qand application .filed February 15, 1882, Serial No. 52,778.

The lime should be burned at a high temperature, prefe rably so high that it is indurated, solidified, andhardened. It is then ground and mixed with tar or othercarbonaceous matter, and while in asemi-pasty condition it is placed in the furnace andthe bottom made by ramming the material in place. I

I prefer to use lime-brick for the. sides and roof of the metal chamber; but when this is t not practical the furnace walls and roof may be made of other brick. In the latter case I place a layer of coke-dust, ,plumbago, or other carbonaceous matter between the lime lining and the brick walls of the furnace, in. order to prevent thelime and the brick from fluxing each'other; or instead of the carbonaceous matter the oxide of chromium or any other highly infusible basic material maybe used. It will be understood that I do not claim this particular construction of furnace as my invention. 1 v 8 When the furnacehas been thus lined and soon as the oxide and metal have become thoroughly fused a chemical action takes place, the silicon of the metal attacking the oxygen of the oxide, the iron of .the oxide going into the metal and the silicon going into the slag as silicic acid, (SiO,.) This first chemical action, which'I term the silicon'period,, will continue from three to five hours, according to the amount of silicon in the metal. During this silicon period but little gas is evolved, hence but little ebullition takes place, the metal being consequently in a comparative state of rest. When the silicon has been eliminated, the carbon is attacked by the oxygen of the oxide and carbonic oxide is formed.

This being a gas, it causes ebullition and the metal boils. This boiling-period, in which the carbon is being eliminated, will last from two to three hours, according to the percentage; of carbon in the initial charge.

When the boiling ceases and the carbon is eliminated, the slag should be tapped off, as it will then contain all the silicic acid resulting from the oxidation of the silicon of the metal. As

soon as the slag is tapped oil a fresh charge of about-ten per cent. of fresh oxide should be charged. This may be oxide of iron alone,

or a mixture of oxide of iron and lime.- The oxygen of the oxide will then attack the phosphorus and-oxidize it to phosphoric acid, (P 0 which will unite with oxide of iron and abide in the slag as a phosphate. When the phosphorus has been thus eliminated, the phosphoritic slag should be tapped off and the rectal deoxidized by the use of speigel, ferromanganese, or silicon, as a silicious pig or a ferro silicide, and the metal then run into the ladle and molds or the metal may (minus thephosphoriticslag) be runinto the ladle and deoxigenated therein. Ineither case care should-be taken to separate the metal from the phosphoritic slag before making the final charge for deoxigenating, as a portion of the carbon in the final charge will be changed to carbonic oxide, (0 which will reduce any phosphate there may be in the slag and cause the phosphorus to go back into the metal.

The time required to perform the aforementioned method Will be about ten hours; but when scrap-iron or scrap-steel can be obtained to advantage the initial charge of' cast-iron need not be more than three or four tenths of the whole weight per heat. In this case the oxide is omitted, and wrought-iron or steelscrap (preferably heated) is put into the molten metal from time to time until the I full charge is made. By this method, the scrap having no silicon and but little carbon in it,

, the average amount of silicon and carbon in the whole charge will be greatly reduced and the oxide coating of the scrap will rapidly desiliconize and] decarburize the metal and expedite the practice, so that a heat may be madein this manner in much less time than when pig and ore only are used. When the heat formed of pig and scrap is thoroughly desiliconized and decarburized the silicious slag should be withdrawn and from five to ten per cent. of oxide'charged and the metal dephosphorized, then removed from the slag and deoxigenized, as before explained.

Gare shouldbe taken that the metal shall be kept in a highly fluid condition during the '.entire process'fthat the oxide employed should LbeLas-free from silica and r phosphoric acid as possible, and that no carbonic oxide, and as little silicic acid as possible, shall be present during the dephosphorizing period, as both carbonic oxide and silicic acid will reduce the phosphate and cause the phosphorus to go back into the metal.

The metal-chamber should be carefully ex amined after withdrawing each heat, and where the lining has wasted away, either on the sides or the bottom, a portion of the mixture of tar and well-burned lime should be put in and well rammed on the old lining previous to charging a new heat.

When molten iron is kept in a highly fluid condition in the presence of a basic lining until the silicon and carbon have been eliminated, and then subjected to a highly basic bath,

the phosphorus may be entirely removed from the metal to the slag, and the metal be thus converted into ingot iron or steel free from phosphorus.

In this application I do not claim any method of preparing and applying calcareous or calcareous-magnesian linings to furnaces such linings and their preparation beingcovered by 'patents or. pending applications for patents hereinbefore cited. Nor do I claim the prophos'ph'orizing it in presence of a basic bath, such process having been patented by me June 5, 1883, No.27 8,738. Nor do I claim that the use of oxides of iron in connection with an open-hearth furnace in the processof purifying iron or steel is new; but

What I do claim is- I 1. Thewithin-described process for converting iron into steel, which consists in, first,

charging the metal, together with suitable methem 'at a high temperature until the silicon "and suitable oxides of iron and maintaining and carbon are eliminated; second, tapping off the silicious slag; third, adding a second charge of suitable .oxides and heatinguntil the phosphorus is eliminated, fourth, tapping of the phosphoritic slag; fifth, deoxidizing and recarburizing the metal apart from the slag, substantially. as and for the purposes described.

JACOB REESE.

Witnesses:

J. BOURKE, J AMES SIPPEY.

cess of desiliconlzing or decarbonizing 1'11 asilicious-lined vessel and then conveying the 'iron into a basic-lined vessel and therein de- 

